How to Do Rock Tumbling

Rock tumbling produces smooth, shiny stones.

Rock tumbling is a hobby for geology enthusiasts. Rock tumbling enthusiasts collect rocks, then use a device called a rock tumbler to grind the rocks down to a smoother shape and polish them. Rock tumbling is a lengthy process. The rocks need to stay in the tumbler for a week or longer for each cycle. First, they are shaped, then they are smoothed and finally they are polished.

Things You'll Need

• Rock tumbler
• Rocks
• Coarse grit
• Water
• Colander
• Bucket
• Garden hose
• Paper towels
• Fine grit
• Tumbling pellets
• Pre-polish grit
• Rock polish

Instructions

Coarse Grit

1. Fill the tumbler barrel at least halfway full of rocks, but no more than ¾ of the way full. Too few or too many rocks could cause the tumbler to either not work properly or to become too heavy.

2. Add coarse tumbler grit. Review the instructions from the tumbler's manufacturer regarding how much grit to add. In general, however, if you have a three lb. barrel size, add four tbsp. of coarse grit.

3. Add water to the tumbler barrel. The water level should be just below the top layer of rocks.

4. Clean and dry both the inside and outside rims and edges of the barrel and its lid. Seal the barrel and turn the device on. Leave the tumbler running constantly for a week. If you feel the urge to check on your rocks, clean and dry the rims and edges again to form a good seal on the barrel before closing it.

5. Place a colander inside a bucket. Pour the barrel in the colander when it is finished tumbling. Never pour slurry from a tumbler down your drain, as it will harden and clog it. Use a garden hose to rinse your rocks and dispose of the slurry outside. Inspect the rocks. If you would like them to be rounder, repeat the process for coarse grit tumbling.

6. Clean your tumbling machine thoroughly. Use paper towels to remove all slurry and debris from the barrel and the seal.

Fine Grit

1. Place your rocks in the barrel. If you do not have enough rocks to fill at least half the barrel, do another batch of coarse grit rocks. Add fine grit to the barrel, following your manufacturer's instructions. For example, if you have a three lb. barrel, add four tbsp. of fine grit. Add enough water to leave the top layer of rocks just above the water line.

2. Dry the edges and rims and seal the barrel. Turn the tumbler on and let it run constantly for one week.

3. Remove the rocks and follow the same cleaning procedure as before for the rocks and the tumbling machine.

Pre-Polish and Polish

1. Replace the rocks in the barrel and add tumbling pellets to help provide cushioning for the rocks. Add water to just below the top layer. Add pre-polish grit, also called extra-fine grit, according to the manufacturer's directions. For example, if you have a three lb. barrel, add five tbsp. of extra-fine grit. Seal the barrel and allow it to run constantly for a week.

2. Remove the rocks and clean them and the machine with the same procedure as before. Separate the pellets by placing the rocks in clean water. Skim the pellets off the top when they float up.

3. Add the rocks back into the barrel, then add enough plastic pellets to achieve a barrel load of 2/3 to ¾. The pellets provide cushioning and prevent scratches. Add the appropriate amount of rock polish according to the manufacturer's recommendations. Or, if you have a three lb. barrel, add five tbsp. of rock polish.

4. Turn the tumbler on and allow it to run constantly for 10 days. Clean the rocks and the machine as before, then allow the rocks to dry. They will appear smooth and shiny even when they are dry.

References

• Geology.com: Rock Tumbler Instructions

Resources

• Rock Tumbling Hobby